The principles of induction heating are well-known; where the inductive process generates eddy currents within conducting material. For example it is used in cooking, a primary coil emitting a changing magnetic flux that induces heat within the substance of conducting food containers to provide a clean, safe, contained and controllable heat. Existing power supplies tend to radiate untoward levels of spurious frequencies while working and require rather specialised power semiconductor devices. They are insufficiently cheap and economical for widespread use as in domestic cooking, although any technique that applies heat so specifically to the cooking vessel should be more desirable and efficient than, for example, a flame. Inductive heating is also used in manufacture, as in zone refining, or the case hardening of gear teeth.
The principles of inductive transfer of electricity for supplying motive power along a defined route or track are also well known but development of this field has been hampered by the difficulty of generating and distributing alternating current electricity of a suitable power and frequency.
Inductive transfer has often been proposed for situations wherein conventional cables and connectors are unsuitable; perhaps for reasons of explosion hazards caused by sparks in operating theatres, or water with attendant shock hazards in underwater applications (like swimming pools), or other sites where the tangle of a multiplicity of power leads is undesirable.